1) large diversity in living things 2) the animal bones were different from those on other countries
Darwin's observations while visiting South America
a group of similar organisms that can mate with each other and produce fertile offspring
1) Some animals were different than those on South America 2) large diversity of life forms
Darwin's observations in the Galapagos Islands
Blown out to sea during a storm or set adrift on a fallen log
How did Darwin think plants and animals had originally come to the Galapagos Islands?
a trait that helps an organism survive and reproduce
the species gradually changed over many generations and became better adapted to the new conditions
Describe Darwin's theory of evolution
The gradual change in a species over time
1) observations between similarities and differences of a species 2) observations of domestic animals selectively bred to have desired traits
Darwin proposed his theory of evolution based on two main things
the process by which individuals are better adapted to their environment are more likely to survive and reproduce than other members of the same species
Darwin explained evolution occurs by natural selection. Define natural selection
Overproduction, competition, variation
Name the three factors that affect natural selection
more offspring are produced than can possibly survive
offspring must compete with each other for food and resources
any difference between individuals of the same species
over a long period of time, natural selection can lead to...
gradually accumulate in a species, while unfavorable ones disappear
1) the shuffling of alleles in meiosis 2) mutations in genes
Where do variations come from?
When a group of individuals remains separated from the rest of its species long enough to evolve different traits
How do new species form?
when sediment covers a dead organism; years and years later, the sediment presses together and hardens into rock
How are fossils formed in sedimentary rock?
fossils that form when remains of an organism in sedimentary rock are soaked by minerals dissolved in water; the minerals replace the remains, forming a petrified fossil
How are petrified fossils formed?
A mold is a hollow space in sediment in the shape of an organism or part of an organism, while a cast is a copy of the organism.
Contrast a mold and a cast.
tar, sap, and ice
Name three substances beside sedimentary rock organisms can be preserved in.
By looking at the layers in the rock; the "younger" layers are closer to the top, and the "older layers" are closer to the bottom, and in the same way, fossils closer to the top are younger than those towards the bottom
How is relative dating used to determine the general age of a fossil?
By looking at the radioactive elements in the rock near the fossil; scientists can compare the amount of a radioactive element in a sample to the amount of the element into which it breaks down. This info can be used to calculate the age of the rock, and therefore the age of the fossil
How is absolute dating used to determine the actual age of a fossil?
the millions of fossils that scientists have collected
What is the fossil record?
evolution occurs slowly but steadily
What does the theory of gradualism say?
species evolve during short periods of rapid change separated by long periods of no change
What does the theory of punctuated equilibria say?
fossils, similarities in body structure, similarities in early development, DNA
What are 4 evidences of evolution?
preserved imprints or remains of living things. found in sedimentary rock.
Similar structures inherited form a common ancestor in related species
What are homologous structures?
in earliest stages of development, the more similar the organisms look, the more related they are.
How are similarities in early development used to support evolution?
species inherit genes from common ancestor
How is DNA used to support evolution?
any change in a gene or chromosome
a type of rock that forms when sediments are pressed and cemented together
A fossil in which minerals replace all or part of an organism
A technique used to determine which of two fossils is older
A technique used to determine the actual age of a fossil